precipitation falls in a watershed in the form of
rain or snow, much of the water filters into the ground.
This process of filtration helps purify the water
that ends up as ground water, which may later end
up being the water coming out of a drinking well,
irrigation pump, or natural spring.
Vegetation and topsoil are
keys to maintaining a healthy filtration system that
benefits people, animals, fish, and plants.
In streams and rivers, large woody debris and rocks
help to further filter and purify the water by slowing
water flow and allowing sediment and suspended pollutants
to settle to the stream bottom. In addition, these
structures within a stream help to reinforce the structure
of a stream, which helps reduce the impact of flooding.
They also serve fish and other aquatic species as
protection from predators, swift currents, and damaging
rays of sunlight, while also providing sources for
food and foraging.
and woody debris help to filter sediments by trapping
behind hundred or thousands of tiny dams or strainers.
Vegetation alongside streams helps to filter sediments
and pollution before they reach the stream, reducing
the impact of erosion fromother parts of the watershed.